The present invention relates generally to blood pressure evaluation procedures and more particularly to non-invasive techniques for determining certain waveform information associated with blood pressure.
The most reliable ways presently known for obtaining information relating to an individual's blood pressure require invasive procedures. Such procedures are not carried out routinely but only under extreme circumstances, for example during heart surgery. Under less critical conditions, blood pressure information including specifically an individual's systolic (maximum) and diastolic (minimum) blood pressures is obtained non-invasive. There are two well known non-invasive techniques presently being used today, one is commonly referred to as auscultation and the other is based on oscillometry. Both of these non-invasive techniques use the standard arm cuff which most people are familiar with. However, in the auscultatory method, the systolic and diastolic pressures are determined by listening to certain sounds (Korotkoff sounds) which occur as a result of the cuff first being pressurized and then depressurized whereas oscillometry actually measures changes in pressure in the cuff as a result of changes in blood pressure as the cuff is first pressurized and then depressurized.
As will be seen hereinafter, the various embodiments of the present invention are based on oscillometry. In order to more fully appreciate these embodiments, reference is made to applicant's own U.S. Pat. No. 3,903,872 (the Link patent) for obtaining blood pressure information non-invasively. This patent which is incorporated herein by reference describes, among other things, a way of obtaining the diastolic pressure of an individual in accordance with a technique which will be discussed in more detail hereinafter. In U.S. Pat. Nos. 4,009,709 and 4,074,711 (Link et al) which are also incorporated herein by reference, non-invasive techniques using oscillometry are disclosed for obtaining the systolic pressure of an individual. These techniques will also be discussed hereinafter.